when the alternating pressure 40Khz ultrasonic cleaner amplitude exceeds the liquid static pressure which will appear negative pressure in the cleaning fluid ,negative pressure that exceed the liquid strength in order to produce cavitation. The minimum sound intensity or sound pressure amplitude that causes liquid to cavitate that is called the cavitation threshold. Various liquids have different cavitation thresholds, and the intensity of the best inexpensive automotive ultrasonic cleaning tank is higher than the cavitation threshold to generate ultrasonic cavitation. For normal liquids, the cavitation threshold digital heated medical ultrasonic cleaner is about 1 / 3W. cm -2 (squared sound pressure proportional to the sound intensity). When the sound intensity ultrasonic cleaner with steamer increases, the ratio of the maximum radius of the cavitation bubbles to the initial radius increases, and intensity of the cavitation increases, that is the higher than sound intensity, the more is the intense the cavitation, which is good for the cleaning effect. But the sound intensity is too high, will produce a lot of useless bubbles, increased the scattering attenuation and the formation of sound barrier, while ultrasonic jewellery cleaner with digital timer is increasing the sound intensity that increase the nonlinear attenuation, it will weaken effect of the cleaning from the sound source. For some difficulty to clean the dirt, such as metal surface oxide, chemical fiber spinnerette hole dirt cleaning, you need to use a higher sound intensity, the surface should be cleaned close to the sound source,The use of trough cleaner with a rod-type focusing transducer is direct into the cleaning solution near the cleaning surface cleaning at most of the time .